The subject matter disclosed herein relates to antennas and, more particularly, to wideband array radiators.
The design and fabrication of high-performance antennas present challenges in the implementation. Important antenna design requirements are wide bandwidth and dual polarization. Other typical design requirements that have been considered in the literature are high directivity as well as small size and ease of manufacturing.
One approach is to form wideband, dual-polarized arrays. A few examples are described below and have generally operated at frequencies of 18 GHz and below. Examples are arrays of flared notches or flared dipoles. Both of these require, for dual polarization, “egg crate” style construction with conductive joints at unit cell boundaries. Millimeter wave versions (e.g., high frequency) have not been attempted due to the difficulties of building the egg crate structure to the requisite tolerances and in forming the conductive joints.
Another approach is a so-called “current sheet” array. These arrays include capacitively-coupled dipoles on a planar layer suspended above a ground sheet by spacers that include the dipole feeds. The spacers are either posts containing multiple coaxial feedthroughs or egg crate assemblies of dielectric cards containing printed feed lines. Millimeter wave version has not been attempted due the high precision required to align the various structures to maintain electrical continuity.
Another type of array includes transverse electromagnetic (TEM) flare antennas. The antennas of such arrays may be referred to as flares or pyramids. In these array types, waves are launched from a conductor (e.g., an inner conductor of a coaxial cable) bridging the gaps between adjacent pyramids. The pyramids are shaped so that the regions between have the shape of a tapered flare. Such antennas may have ultra-wide bandwidth (15:1 has been demonstrated); dual polarization; wide-angle scanning (75° from broadside in all planes has been demonstrated). Millimeter wave versions, however, would be difficult because of the mechanical tolerances in forming the pyramids and in mounting them precisely so that the gaps between them are consistent and present a consistent impedance to the feed lines.